| Abstract |
Since comissioning of Dora I power plant (7.35 MWe) in 2006 reinjection operations have been successfully conducted to ensure sustainability for the Salavatlý geothermal system and prevent environmental pollution. Second plant, Dora II (11.1 MWe) was introduced in 2010, and ever since its wastewater reinjection has been continuing. Another plant, Dora IIIa (17 MWe) was taken into line in August/2013, and its reinjection has also been carrying out. The fourth plant, Dora IIIb (17 MWe) will be commissioned within few months and its reinjection operation has already been planned. Salavatlý is a middle entalpy field (700 kJ/kg), and binary power plants that are used require large amount of geofluids to be handled in renjection operations. Therefore, prevention of cooling effect is very much critical, and special care must be taken to avoid negative effects of reinjection. Several strategies (line drive, margin of the field, etc) had already been examined to conduct successful reinjection in this field. Geoscientific and reservoir engineering aspects of the field have been carefully studied, and finally suitable areas which have lower pressures and temperatures on the margins of the field were selected for each reinjection operation. By this way reinjected waste waters were distributed around the field and cooling hazard was mostly mitigated. Actually, some 2600 ton/h of water were handled in the reinjection systems, and after the fourth plant this would increase to approx. 4000 ton/h which are substantial amount. Eight years of successful 100% reinjection operation so far depended upon correct geoscientific evaluations and continuous monitoring of the field. All important parameters such as bottomhole and/or wellhead pressures, temperatures and gas contents were either periodically or continuously measured and registered. In order to follow reinjected water routes tracer tests have been conducted. Furthermore, a seismogrph grid was installed and micro-seismic monitoring was conducted. So far, pressure measurements in monitoring wells have indicated no pressure decline in the reservoir. And, measurements from the production wells have not pointed out any cooling effect either. In this study, geoscientific and reservoir engineering information will be provided, and all existing and planned reinjection systems are described. PT information from the monitoring will be presented. Finally, results of these operations will be reported. |